Commit 13961a17 authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Luis Henriques

KVM: svm: unconditionally intercept #DB

commit cbdb967a upstream.

This is needed to avoid the possibility that the guest triggers
an infinite stream of #DB exceptions (CVE-2015-8104).

VMX is not affected: because it does not save DR6 in the VMCS,
it already intercepts #DB unconditionally.
Reported-by: default avatarJan Beulich <jbeulich@suse.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 033edc3a
...@@ -1104,6 +1104,7 @@ static void init_vmcb(struct vcpu_svm *svm) ...@@ -1104,6 +1104,7 @@ static void init_vmcb(struct vcpu_svm *svm)
set_exception_intercept(svm, UD_VECTOR); set_exception_intercept(svm, UD_VECTOR);
set_exception_intercept(svm, MC_VECTOR); set_exception_intercept(svm, MC_VECTOR);
set_exception_intercept(svm, AC_VECTOR); set_exception_intercept(svm, AC_VECTOR);
set_exception_intercept(svm, DB_VECTOR);
set_intercept(svm, INTERCEPT_INTR); set_intercept(svm, INTERCEPT_INTR);
set_intercept(svm, INTERCEPT_NMI); set_intercept(svm, INTERCEPT_NMI);
...@@ -1634,20 +1635,13 @@ static void svm_set_segment(struct kvm_vcpu *vcpu, ...@@ -1634,20 +1635,13 @@ static void svm_set_segment(struct kvm_vcpu *vcpu,
mark_dirty(svm->vmcb, VMCB_SEG); mark_dirty(svm->vmcb, VMCB_SEG);
} }
static void update_db_bp_intercept(struct kvm_vcpu *vcpu) static void update_bp_intercept(struct kvm_vcpu *vcpu)
{ {
struct vcpu_svm *svm = to_svm(vcpu); struct vcpu_svm *svm = to_svm(vcpu);
clr_exception_intercept(svm, DB_VECTOR);
clr_exception_intercept(svm, BP_VECTOR); clr_exception_intercept(svm, BP_VECTOR);
if (svm->nmi_singlestep)
set_exception_intercept(svm, DB_VECTOR);
if (vcpu->guest_debug & KVM_GUESTDBG_ENABLE) { if (vcpu->guest_debug & KVM_GUESTDBG_ENABLE) {
if (vcpu->guest_debug &
(KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))
set_exception_intercept(svm, DB_VECTOR);
if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP)
set_exception_intercept(svm, BP_VECTOR); set_exception_intercept(svm, BP_VECTOR);
} else } else
...@@ -1753,7 +1747,6 @@ static int db_interception(struct vcpu_svm *svm) ...@@ -1753,7 +1747,6 @@ static int db_interception(struct vcpu_svm *svm)
if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP)) if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP))
svm->vmcb->save.rflags &= svm->vmcb->save.rflags &=
~(X86_EFLAGS_TF | X86_EFLAGS_RF); ~(X86_EFLAGS_TF | X86_EFLAGS_RF);
update_db_bp_intercept(&svm->vcpu);
} }
if (svm->vcpu.guest_debug & if (svm->vcpu.guest_debug &
...@@ -3722,7 +3715,6 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu) ...@@ -3722,7 +3715,6 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu)
*/ */
svm->nmi_singlestep = true; svm->nmi_singlestep = true;
svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF); svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
update_db_bp_intercept(vcpu);
} }
static int svm_set_tss_addr(struct kvm *kvm, unsigned int addr) static int svm_set_tss_addr(struct kvm *kvm, unsigned int addr)
...@@ -4328,7 +4320,7 @@ static struct kvm_x86_ops svm_x86_ops = { ...@@ -4328,7 +4320,7 @@ static struct kvm_x86_ops svm_x86_ops = {
.vcpu_load = svm_vcpu_load, .vcpu_load = svm_vcpu_load,
.vcpu_put = svm_vcpu_put, .vcpu_put = svm_vcpu_put,
.update_db_bp_intercept = update_db_bp_intercept, .update_db_bp_intercept = update_bp_intercept,
.get_msr = svm_get_msr, .get_msr = svm_get_msr,
.set_msr = svm_set_msr, .set_msr = svm_set_msr,
.get_segment_base = svm_get_segment_base, .get_segment_base = svm_get_segment_base,
......
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